Accumulation and metabolic profile of phenolic compounds (PheCs; serving as UV-screening pigments and antioxidants) as well as carbon fixation rate (A_n) and plant growth are sensitive to irradiance and temperature. Since these factors are naturally co-acting in the environment, it is worthy to study the combined effects of these environmental factors to assess their possible physiological consequences. We investigated how low and high irradiance in combination with different temperatures modify the metabolic profile of PheCs and expression of genes involved in the antioxidative enzyme and PheCs biosynthesis, in relation to photosynthetic activity and availability of non-structural carbohydrates (NSC) in spring barley seedlings. High irradiance positively affected A_n, NSC, PheCs content, and antioxidant activity (AOX). High temperature led to decreased A_n, NSC, and increased dark respiration, whilst low temperature was accompanied by reduction of UV-A shielding but increase of PheCs content and AOX. Besides that, irradiance and temperature caused changes in the metabolic profile of PheCs, particularly alteration in homoorientin/isovitexin derivatives ratio, possibly related to demands on AOX-based protection. Moreover, we also observed changes in the ratio of sinapoyl-/feruloyl- acylated flavonoids, the function of which is not yet known. The data also strongly suggested that the NSC content may support the PheCs production.

Background and Aims: Stomata are pores in the plant epidermis that regulate gas exchange by controlling CO2 uptake and water loss through transpiration. Stomatal conductance, which determines the rate of this gas exchange, is influenced by both the dynamic aperture of individual stomata and stomatal density (StD). It is a matter of discussion whether a single dominant factor that controls StD exists or a combination of several independent factors results in the final StD. Methods: We evaluated the role of photosynthetic photon flux density (PPFD) and internal CO2 concentration (Ci). Plants of Helianthus annuus were cultivated under a gradient of PPFD in the range of 50–510 μmol m−2 s−1; both cotyledons and true leaves were analysed. The independent effects of PPFD and Ci on stomatal traits were assessed using additive linear models controlling for their physiological covariation. Results: The results demonstrate that stomatal development in sunflower leaves is predominantly regulated by PPFD, not Ci. While stomatal traits in cotyledons remained largely unaffected by either PPFD or Ci, true leaves showed a clear and consistent response to light intensity. Additive linear models confirmed that only PPFD had a significant and robust effect on StD, whereas Ci showed no consistent contribution. This supports the interpretation that Ci, although physiologically coupled with PPFD, does not directly control stomatal development. Furthermore, we observed anatomical asymmetry between leaf surfaces: while both adaxial and abaxial sides responded to PPFD, the abaxial surface showed higher sensitivity, with significant effects on both StD and stomatal length. Conclusions: Our findings emphasize light as the key environmental signal guiding stomatal patterning. Additionally, the results revealed varying differences in stomatal development on adaxial and abaxial sides of the leaf in response to light.

Two different sewage sludge (SS) waste materials were commercially co-composted with wood chips (WCh) and grass to determine their conversion potential and elucidate the manner that it is affected by the various process operational parameters. A blend of three different SS streams composted more efficiently in terms of temperature attained during the process than a single SS stream when the materials were co-treated with WCh acting as the bulking agent. WCh facilitated the accomplishment of a temperature over the sanitation limit and concurrently the establishment of a high decomposition rate over a long period. Further increasing the fraction of WCh in the composting mixture had an insignificant effect on the decomposition rate of organics in SS. The presence of grass in a mixture had a negative influence on the composting temperature that retained below the sanitization limits during the entire process. Aeration led to an increment in temperature but in all cases the enhancement remained at levels lower than 20 °C throughout the trials. Concentration of heavy metals in all mixtures was sufficiently reduced with composting regardless of the SS type, mixing ratio, the use of a secondary organic substrate and aeration.